Fluent reading enables readers to focus on gaining meaning from what is read. This crucial facet of reading is often neglected instruction in elementary and is nearly non-existent in middle and high school instruction (Allington, 1983; Rasinski, Padak, McKeon, Wilfong, Friedauer, & Heim, 2005). At the elementary level, fluency instruction focuses on automaticity with decoding, while some research on the secondary level suggests vocabulary may also play a role in fluent reading for adolescents (Carlisle, 2000; Singson, Mahoney, St Maim, 2000). Consequently, instruction in morphology may impact fluency in both decoding and vocabulary. This intervention study examined the relative effects of a morphology intervention on fluency with comprehension for adolescent struggling readers in grades six through eight as part of a tiered response to intervention system. Students were selected for intervention classes on the basis of state criterion-referenced assessment scores that did not meet the 2008 end-of-year standard of a 2100 scale score. The researcher-developed intervention contained morphology instruction for both decoding and understanding word meanings as recommended in the adolescent literacy research. This research shows that morphology may play a dual role in influencing fluency outcomes as it improves both decoding and a knowledge of word meanings. A mixed methods design utilizing quasi-experimental procedures for the quantitative component and an open-ended questionnaire and semi-structured interviews for the qualitative portion was implemented. Assessments included the newly developed Texas Middle School Fluency Assessment and the Test of Morphological Structure, with pretest data acting as the covariate in ANCOVA analysis of fluency. Means and standard deviations were used for the decoding and morphology data to aid in the analysis of the fluency data. For the qualitative portion. open-ended questionnaires and semi-structured interviews for the teacher of the intervention and a random sampling of the treatment students were conducted and analyzed using constant comparison. These data were triangulated with the quantitative data to strengthen the analysis. Results from the study begin an exploration of the role of morphology on adolescents' fluency that informs literacy practices for educators as well as provides initial insight to guide future research in this area. From the quantitative data it appears morphology instruction does benefit adolescents' ability to decode and increases students' comprehension. Fluency was not impacted during the study time frame. Questionnaire and interview data support the findings from the quantitative data and suggest the intervention improved understanding of word meanings as well. An important finding from the interviews suggests that students enjoyed participating in the intervention instruction, which may be especially important with adolescent struggling learners. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]